Compounds having the pyrrolo[2,3-d]pyrimidine skeleton of the formula: ##STR2## are known to have various important pharmacological actions. For example, it is known that antibacterial compounds are substituted by amino groups at both the 2- and 4- positions of the skeleton (see, U.K. Patent 812, 366, and Townsend L. B. et al, J. Med. Chem., Vol. 31, 1501(1988), etc.). and that compounds useful as a herbicide and antibiotic have a primary amino group as the amino group (Okuda et al, Nippon Noyaku-gakkaishi, Vol. 6, 9(1981), Pedersen E. B. et al., Chemica Scripta, Vol. 28, 201(1988), etc.), other known antiviral compounds have an amino group at the 2- and 4- positions as well as a sugar residue at the 7- position of the skeleton (e.g., E.P. Publication No. 57548).
Nevertheless, in particular, pyrrolo[2,3-d]pyrimidine derivatives having an alkyl or alkenyl group at the 7- position, an amino group substituted by alkyl or alkenyl group at the 2- position, and a cyclic amino or chain substituted amino group at the 4- position, have not been described in the prior art.